Ford COUGAR 1968 Shop Manual page 254

7-66
GROUP 7
-
Automatic Transmission
secondary valve will again move out-
ward, closing the governor exhaust
port and opening the line pressure
to governor passage. Above 10 mph,
governor pressure is regulated in this
manner, and will vary with the car'
speeds.
I f
the car speed drops below 10
mph, the primary valve spring will
move the primary governor valve
in, closing the line leakage exhaust
port at the primary .valve. Pressure
in the line leakage passage will be-
come equal to line pressure, forcing
the secondary governor valve in.
This action shuts off line pressure
feed to the governor passage and
exhausts the governor circuit.
When the secondary governor
valve is regulating, governor pressure
is delivered to the end of the:
1. 3-2 timing valve
2. 2-3 shift valve
3. 1-2 shift valve
4. Coasting boost valve
5. Cut back valve
Fig. I I shows the relationship be-
tween governor pressure and output
shaft rpm.
Throttle Booster Valve
Throttle plate openings above 50
degrees provide very little change in
engine vacuum as compared to throttle
plate openings below 50 degrees. The
throttle booster valve is used to boost
throttle pressure and provide the neces-
sary shift delay for engine throttle
plate openings above 50 degrees.
Below approximately 65 psi pri-
mary TV pressure, TV pressure
flows to and through the throttle
boost valve unaffected, working on
the end of the boost valve and on
the area differential in the first valley.
When TV pressure increases above
65 psi, the force created by TV
pressure acting on the end of the
throttle boost valve, minus the force
of TV pressure acting on the area
differential in the first valley will
exceed the force of the spring. This
causes the valve to move against
the spring, closing off primary TV
pressure to the area differential and
permitting this area to be fed from
line pressure, causing a boost in the
pressure used for shift delay only.
Because the area of the end of the
throttle boost valve exceeds the area
differential in the first valley by 3
to I, thrott!e boost pressure above
65 psi primary TV pressure will
increase 3 psi for each I psi increase
in primary TV.
Figure 10 shows the relationship
between primary TV pressure and
boosted throttle pressure.
Throttle Modulator Valve
The throttle modulator valve, lo-
cated in the end of the 2-3 shift valve
bore reduces throttle pressure which
acts on the end of the 2-3 shift valve
and on the area differential of the 1-2
shift valve. Modulated throttle pres-
sure in these areas provides shift
delay in relation to throttle opening.
Cutback Valve
Increased line pressure is required
to prevent, clutch and band slippage
under stall conditions. Dependent up-
on vehicle speed, the requirements for
increased line pressure are considerably
reduced. When governor pressure act-
ing on the end of the cutback valve ex-
ceeds the force of TV pressure acting
on its area opposing governor, the cut-
back valve will move cutting off pri-
mary TV pressure being fed to the
lower valley of the pressure booster
valve, thru the coasting boost valve.
This action reduces the assist that the
pressure booster valve provides to the
main regulator valve spring. The cut-
back valve movement will therefore
vary with engine throttle opening and
vehicle speed. Figure I I shows how
line pressure varies with output shaft
rpm (vehicle speed) at constant vac-
uum values.
Line Pressure Coasting Regulator
Valve
When the selector lever is moved
from D to 2 or
I
to force a 3-2
(closed throttle) downshift in order to
use the engine as a brake, additional
pressure may be required to insure
positive band applications. With the
throttle closed there will be no TV
pressure present at the pressure boost-
er valve. At speeds above approxi-
mately 30 mph, the required additional
pressure is obtained through the use
of the coasting regulator valve. When
the manual valve is shifted from D to 2
(second gear hold) or 1 (manual low),
line pressure is exhausted from the end
of the coasting regulator valve, allow-
ing governor pressure to move the
valve train downward in the bore. This
allows line pressure to pass through the
lower valley of the valve to the lower
valley of the pressure booster valve,
increasing main line pressure. As
line pressure tends to increase, the
higher pressure working on the dif-
ferential area of the coasting regulator
valve causes the valve to move up:
wards. This causes .the supply of line
pressure to the pressure booster valve
to be cut off, and line pressure is
again reduced. The valve continues
this regulating cycle until the vehicle
has slowed down to the point where
governor pressure, acting on the end
of the valve, is no longer sufficient
to overcome the force of line pressure
acting on the area differential. In this
manner boost in line pressur? is re-
gulated by vehicle speed, the higher
the speed, the higher the pressure
(above approximately 30 mph.) (Fig.
12).
1-2 Shift Valve Train
The 1-2 shift valve train is com-
posed of the 1-2 shift valve, the D2
valve, and the 1-2 shift valve spring.
D Range. In D range the 1-2
shift valve is held closed (up) by
modulated throttle pressure acting
on the differential area between the
two lands of the 1-2 shift valve, by
D fluid pressure acting on the differ-
ential in area between the two lands
at the spring end of the D2 valve, and
by the 1-2 shift valve spring. Gover-
nor pressure tends to move the 1-2
shift valve train against these forces.
When force created by governor pres-
sure exceeds the forces holding the
1-2 shift valve train closed, the 1-2
shift valve and D2 valve will be
opened (move downward), closing
the exhaust port and allowing D fluid
to pass through the D2 valve to ac-
complish the 1-2 shift. When the D2
valve is moved downward, D fluid is
exhausted from the differential in
areas provided by the lower two lands
of the D2 valve and modulated
throttle pressure from area differ-
ential on 1-2 valve. This action elimi-
nates the force created by D fluid
which tends to hold the 1-2 shift valve
train closed.
If gcvernor pressure is reduced to
the point where spring force exceeds
governor pressure force, the 1-2 shift
valve train will move up (close) cut-
ting off the flow of D fluid through
the valve and opening the exhaust
port allowing a downshift to low gear.
If the throttle is opened through
detent, the downshift valve moves to
allow line pressure to enter the mo-
dulated throttle pressure passage at
the 1-2 shift valve to provide a
forced 2-1 downshift.
1 Range. Once the transmission is
in low gear I-R fluid, which is di-
rected to the D2 valve, passes through
the D2 valve and is delivered to the
spring end of the D2 valve, prevent-
ing an upshift I-R fluid which passes
through the D2 valve also applies
the reverse clutch. Coasting down-
shifts to first gear are not possible
above approximately 30 mph in !ow
range.
2 Range. In 2 range, 2 fluid is